1. Field of the Invention
The present invention relates to a projector.
2. Description of Related Art
There has been known a projector that modulates a light beam irradiated by a light source in accordance with image information to form an optical image using an optical modulator and projects the optical image on a screen in an enlarged manner using a projection optical device (see Related art document JP2002-365720A).
In this projector, a display size to be projected can be adjusted with use of an electronic zoom function (which is designed to change the display size by utilizing not a lens but a circuit) based on, for example, specified zoom, specified aspect ratio and specified resolution that are set and input by a user.
The electronic zoom function is capable of changing the size of a projection image projected on a screen by performing a predetermined processing on image information and changing the size of an optical image formation area within a valid area available to form the optical image in the optical modulator. With the electronic zoom function, the formation area is generally so enlarged or reduced to be symmetric with respect to a center position of the valid area in the optical modulator while keeping the center position fixed.
The projector disclosed in the above Related art document projects the projection image on the screen with the setting position of the projector being fixed. When the projection image is enlarged or reduced using the electronic zoom function, the formation area is so enlarged or reduced to be symmetric with respect to the center position of the valid area in the optical modulator while keeping the center position fixed. Therefore, the projection image is enlarged or reduced while the center position of the projection image projected on the screen is substantially matched with the center position of the screen.
However, once the setting position of the projector is changed with respect to the screen, the center position of the projection image projected on the screen is misaligned with the center position of the screen. Accordingly, the center position of the projection image cannot be matched with the center position of the screen even by enlarging or reducing the projection image using the electronic zoom function.
To avoid such problem, a method for changing the position of the projection image on the screen by changing the relative position between the optical axis of the projection optical device and the optical axis of the light beam passing through the optical modulator is suggested.
However, this method needs to employ a configuration for moving the projection optical device along an optical image formation plane of the optical modulator in the vertical and horizontal directions, and therefore requiring construction of a structure or mechanism for accurately moving the projection optical device in the vertical and horizontal directions.